Prevalence and growth of Listeria monocytogenes in naturally contaminated seafood

Listeria monocytogenes contamination of seafood varies with product category. The highest prevalence was found in cold-smoked fish (34-60%), while the lowest was found in heat-treated and cured seafood (4-12%). The prevalence of L. monocytogenes differed greatly in cold-smoked salmon between production sites, ranging from < 1.4% (nil out of 70 samples) to 100%. The prevalence at the individual production sites was reproducible at repeated sampling. The results indicate that it is possible to produce cold-smoked salmon with a low prevalence of L. monocytogenes. The organism showed moderate growth in naturally contaminated cold-smoked, and 'gravad', fish while the growth appeared faster in hot smoked fish. Thus L. monocytogenes is not under control in these products. Finally, the prevalence and growth of L. monocytogenes in naturally contaminated cold-smoked salmon are discussed in relation to controlling this risk.